The embodiments disclosed herein are directed to biomedical patches for repairing tissue defects, such as dural defects, and delivery systems applicable to same.
The human brain and spinal cord are surrounded by a system of three protective membranes known as the meninges: the pia mater, the arachnoid mater, and the dura mater. The meninges serve to maintain a layer of cerebrospinal fluid around the brain and spinal cord, protect the brain and spinal cord from trauma/abrasion, and support extra-cortical vasculature carrying blood to/from the brain. The dura mater is a thick fibrous membrane lining the inner surface of the skull and spinal column which forms a water-tight sac around the central nervous system and serves as the primary barrier between nervous tissue and the underlying bone. Given the critical role of the dura mater in maintaining a closed layer of cerebrospinal fluid around the brain and spinal cord, and in protecting cortical tissue from physical damage/irritation, the health, patency, and structure of the dura mater is essential to proper cortical functions.
The dura mater may sustain insults, injuries, or defects by accident, trauma, disease, or through routine surgical procedures. During the course of standard neurosurgical procedures the dura mater is commonly incised, resected, removed, or disrupted and must be repaired intraoperatively. In a large percentage of neurosurgical procedures surgeons must access anatomical sites within the skull, brain, spinal cord, and spinal column requiring disruption of the native dura mater. In the case of minimally invasive neurosurgical procedures (e.g. burr hole, shunt placement, ablation, etc.), the dura mater may only be minimally incised (defect <1 cm2) to pass small tools into the underlying nervous tissue. In the case of more invasive neurosurgical procedures (e.g. decompressive craniotomy, tumor excision, trauma, etc.), the dura mater may be vastly resected or completely removed (defects >1000-1500 cm2) to allow for cortical decompression or removal of diseased tissues. In all cases, regardless of the size or location of the dural defect, the dura mater must be repaired intraopertatively in order to restore the protective covering of the brain and reestablish the continuous layer of cerebrospinal fluid around the central nervous system. To facilitate this repair surgeons employ a type of surgical membrane or patch known as a “dural substitute.”
Dural substitutes may comprise any type of material utilized to repair or replace the dura mater and promote healing and/or regeneration of native dura, a process known as “neoduralization”. In all instances dural substitutes must cover the dural defect, enable a water-tight seal of dural defect, and provide a suitable scaffold for the ingrowth of native dural fibroblasts. As a result the majority of dural substitutes comprise a planar material which may be sutured into the native dura or passively draped over the dural defect to close the dural defect.